1.Field of the Invention
This invention relates in general to a method and apparatus for avoiding communication protocol errors where a plurality of master nodes are present on a serial bus and in particular to a method and apparatus for resolving multi-master nodes on a train communication system which uses high level data link control (HDLC) communication equipment with DIN 43322 specification.
2. Description of the Related Art
A train communication system is being developed by the assignee of the present application which, based on the proposed European specification DIN 43322 for "Serial Interfaces to Programmable Electronic Equipment for Rail Vehicles," incorporated herein by reference, enables a master node located typically in a head car of a train to communicate via a serial bus to slave nodes on middle cars of the train and on a tail car of the train. See also, "International Standard-Information processing systems-Data communication-High-level data link control elements of procedures, ISO 4335", Third edition, Global Engineering Documents, Irvine, Calif., 1987, the subject matter of which is also incorporated herein by reference. However, trains are often reconfigured and rearranged by, for example, hooking one train up to the last car of another train resulting in a multi-master train communication system. The train communication systems of the two respective trains, now joined, thus have a conflict as to which master node becomes the overall master node for the newly configured train. There is a need for each of the original train communication systems to have the capability of resolving this conflict to provide an overall train communication system with an overall master node.